A mesh-type SVG power unit circuit

Abstract

This utility model discloses a grid-type SVG power unit circuit, belonging to the field of power electronics technology. The circuit includes an overcapacitor unit, a main control unit, and a bypass control unit. The first transmission terminal of the overcapacitor unit connects a voltage sampling unit, a resistive charging / discharging unit, an EMI filter, a supporting capacitor unit, a power take-off and transfer unit, and a rectifier unit in parallel via an isolating switch. The second transmission terminal is connected to the power take-off and transfer unit. The rectifier unit is connected to an external copper busbar via the bypass control unit, and the power take-off and transfer unit supplies power to each unit. This utility model, through multi-module collaborative design, achieves dual-path intelligent power supply switching, graded current-limiting charging / discharging control, rapid bypass fault isolation, overcapacitor master-slave collaborative management, and bidirectional energy conversion, improving power supply stability, charging / discharging accuracy, system fault tolerance, and dynamic response capability. Simultaneously, the modular layout and optimized heat dissipation design enhance engineering practicality and effectively meet the high-performance requirements of modern power systems for SVG devices.

Description

Technical Field

[0001] This utility model belongs to the field of power electronics technology, and in particular relates to a grid-type SVG power unit circuit. Background Technology

[0002] In the power system field, SVG (Static Var Generator) is a key power electronic device mainly used for reactive power compensation and grid stability control. It plays a vital role in maintaining power system voltage stability, improving power quality, and enhancing system dynamic response capabilities. With the continuous expansion of power system scale and the widespread integration of distributed power sources, higher requirements are placed on the performance and reliability of SVG, especially its core power unit circuit.

[0003] Existing SVG power unit circuits suffer from numerous problems in practical applications. For example, in the power supply stage, the power supply design of some circuits is not flexible and efficient enough, failing to stably provide the required power according to different operating conditions, thus affecting the stability of equipment operation. In terms of charge and discharge management, traditional resistive charge and discharge units have simple structures, making it difficult to accurately control the current during charging and discharging, which can easily lead to overheating of the equipment, posing safety hazards and reducing the equipment's lifespan. The bypass control unit has a slow response speed during fault handling, failing to quickly achieve fault isolation and system reconfiguration, reducing the system's fault tolerance and operational reliability. Furthermore, existing supercapacitor units have low functional integration, failing to fully utilize the advantages of supercapacitors and limiting the improvement of the overall performance of SVG. Therefore, there is an urgent need to develop a new type of grid-type SVG power unit circuit to overcome the shortcomings of existing technologies and meet the growing needs of modern power systems. Utility Model Content

[0004] This invention proposes a grid-type SVG power unit circuit to address problems in existing technologies such as inflexible power supply, coarse charge / discharge control, slow bypass response, and low supercapacitor integration. Through multi-module collaborative design and functional optimization, this invention offers significant advantages in power supply reliability, charge / discharge accuracy, fault handling efficiency, and system integration.

[0005] The above objectives are achieved through the following technical solutions:

[0006] A grid-type SVG power unit circuit includes an overcapacitor unit, a main control unit, and a bypass control unit. The overcapacitor unit has a first power supply terminal and a second power supply terminal. The first power supply terminal is connected in parallel via an isolating switch to a voltage sampling unit, a resistive charging and discharging unit, an EMI filter, a supporting capacitor unit, a power extraction and conversion unit, and a rectifier unit. The second power supply terminal is electrically connected to the power extraction and conversion unit. The voltage sampling unit, the resistive charging and discharging unit, the EMI filter, and the rectifier unit are electrically controlled and connected to the main control unit. The rectifier unit is connected to external copper busbar A and external copper busbar B via the bypass control unit. The power extraction and conversion unit is connected to the main control unit, the bypass control unit, and the overcapacitor unit for power supply.

[0007] Preferably, the power supply conversion unit includes a first switching power supply, a second switching power supply, and a dual-power supply module; the first input terminal of the dual-power supply module and the input terminal of the second switching power supply together serve as the first power supply port of the power supply conversion unit and are connected in parallel with the supporting capacitor unit; the second input terminal of the dual-power supply module serves as the second power supply port of the power supply conversion unit and is connected to the second power transmission terminal of the supercapacitor unit; the input terminal of the first switching power supply is connected to the output terminal of the dual-power supply module; the output terminal of the first switching power supply is the first conversion power supply terminal of the power supply conversion unit, and the output terminal of the second switching power supply is the second conversion power supply terminal of the power supply conversion unit.

[0008] Preferably, the supercapacitor unit includes a photoelectric conversion module, a supercapacitor operating power terminal, an optical fiber signal transmission port, a main controller, several supercapacitor modules, and the same number of slave controllers as the supercapacitor modules; the slave controllers are electrically connected to the supercapacitor modules one-to-one; all slave controllers are connected in parallel based on the signal transmission ports and then connected to the control port of the main controller; the communication port of the main controller is connected to the optical fiber signal transmission port through the photoelectric conversion module; the photoelectric conversion module, the main controller, and all slave controllers are connected in parallel based on the operating power ports and then connected to the supercapacitor operating power terminal; the two ends of all supercapacitor modules connected in series are connected to the first power transmission terminal and simultaneously connected to the second power transmission terminal.

[0009] Preferably, the resistive charging and discharging unit includes a charging circuit and a discharging circuit; one end of the charging circuit is connected to the negative terminal of the first power supply terminal of the supercapacitor unit through the isolating switch, the other end of the charging circuit is connected to one end of the charging circuit, and the other end of the charging circuit is connected to the positive terminal of the first power supply terminal of the supercapacitor unit through the isolating switch; a current sensor mounting point is provided between the charging circuit and the discharging circuit.

[0010] Preferably, the charging circuit includes an equivalent resistor I, an equivalent resistor II, a contactor III, and a reactor connected in series; a contactor IV is connected in parallel across the two ends of the equivalent resistor I; and a diode is connected in parallel across the two ends of the series circuit formed by the equivalent resistor I, the equivalent resistor II, and the contactor III.

[0011] Preferably, in the charging circuit: the equivalent resistance I is composed of a first resistor and a second resistor connected in parallel; the equivalent resistance II is composed of a third resistor, a fourth resistor, a fifth resistor, and a sixth resistor connected in series.

[0012] Preferably, the discharge circuit is composed of resistor III, resistor IV and resistor V connected in series.

[0013] Preferably, the bypass control unit includes a bypass control board, bypass contactor I, and contactor II. The power supply terminals of the bypass control board are electrically connected to the power supply transfer unit. The coil of contactor II and the auxiliary contacts of contactor II are respectively connected to the bypass control board. The series circuit of the auxiliary contacts of contactor II and the coil of bypass contactor I is electrically connected to the power supply transfer unit. The rectifier unit is connected to external copper busbar A and external copper busbar B through bypass contactor I.

[0014] Preferably, the rectifier unit includes an IGBT upper bridge unit, an IGBT lower bridge unit, a first IGBT adapter unit, and a second IGBT adapter unit; the IGBT upper bridge unit and the IGBT lower bridge unit are connected in parallel, and the IGBT upper bridge unit contains four or six IGBT modules, while the IGBT lower bridge unit contains the same number of IGBT modules as the IGBT upper bridge unit; all IGBT modules in the IGBT upper bridge unit are respectively connected to the first IGBT adapter unit, and all IGBT modules in the IGBT lower bridge unit are respectively connected to the second IGBT adapter unit; an absorption capacitor unit I is connected in parallel across the two ends of the IGBT upper bridge unit, and an absorption capacitor unit II is connected in parallel across the two ends of the IGBT lower bridge unit.

[0015] Preferably, the bypass contactor I includes normally open contacts and normally closed contacts that are interconnected; the IGBT upper bridge unit is directly connected to the external copper busbar A, and the IGBT lower bridge unit is connected to the external copper busbar B through the normally closed contact of the bypass contactor I; the external copper busbar A is connected to the external copper busbar B through the normally open contact of the bypass contactor I.

[0016] Preferably, the main control unit includes a unit control board, a drive signal adapter board, a first IGBT drive board, and a second IGBT drive board; the drive signal adapter board is electrically connected to the unit control board, and is also electrically connected to the first IGBT adapter unit through the first IGBT drive board, and electrically connected to the second IGBT adapter unit through the second IGBT drive board; the voltage sampling unit, the resistive charging and discharging unit, and the EMI filter are respectively electrically connected to the unit control board.

[0017] The beneficial effects of this utility model are:

[0018] 1) Dual-path intelligent switching enhances power supply stability and flexibility. The power supply unit employs a dual-path power supply module, automatically switching between the main power supply and the backup power supply. Under normal operating conditions, power is drawn from the main circuit; in case of a fault, it seamlessly switches to the overcapacity backup power supply, ensuring uninterrupted power supply to core components such as the main control unit and bypass control unit. The first and second switching power supplies are partitioned: DCPW1 provides stable power to the core control unit, while DCPW2 supplies power to non-critical loads, achieving power priority management and improving the system's anti-interference capability.

[0019] 2) Graded current limiting control for precise current regulation and safety. The charging circuit features a two-stage current limiting design: during the first stage of charging, equivalent resistor I and equivalent resistor II are connected in series to limit the initial current; during the second stage of charging, equivalent resistor I is short-circuited, and only equivalent resistor II limits the current. This, combined with the switching between contactor III and contactor IV, achieves segmented voltage control, limiting charging time and preventing current surges. The discharge circuit uses multiple resistors in series: resistors III, IV, and V are connected in series to form the discharge circuit, ensuring rapid discharge of the overcapacitor unit and supporting capacitor before maintenance, eliminating the risk of residual charge. Enhanced protection mechanisms include a parallel diode freewheeling in the charging circuit to suppress back electromotive force when the reactor is de-energized, preventing component damage; a monitoring interface is reserved at the current sensor installation point, allowing for current monitoring through power conversion even without actual installation, thus improving safety.

[0020] 3) Rapid response isolation enhances system fault tolerance and reliability. The bypass control unit employs a mechanical bypass control board + dual contactor linkage structure: After receiving fiber optic commands, the mechanical bypass control board triggers the bypass contactor I via contactor II. The normally closed contact disconnects the isolation rectifier unit, and the normally open contact closes to form a copper busbar direct bypass. This short response time ensures rapid fault isolation. The bypass contactor contact linkage design ensures that during normal operation, the IGBT lower bridge unit is connected to the external copper busbar B via normally closed contacts; in case of a fault, the normally open contacts close the bypass rectifier unit, maintaining system power transmission and preventing system paralysis due to a single power unit failure.

[0021] 4) High-integration management, enhancing energy storage and inertia support capabilities. Master-slave controller architecture: A master controller and slave controllers correspond one-to-one with the supercapacitor modules, monitoring parameters such as voltage, current, and temperature in real time. Parallel communication via the SPI bus enables balanced management and fault warning across all modules, improving energy storage efficiency and lifespan. Photoelectric conversion and fiber optic communication: The master controller connects to the fiber optic port through a photoelectric conversion module, converting electrical signals into optical signals for transmission. This provides strong resistance to electromagnetic interference, ensuring stable data interaction between the supercapacitor unit and external systems, supporting rapid release of active power during grid faults, and providing inertia support. Series module energy storage optimization: Multiple supercapacitor modules are connected in series to form a high-capacity energy storage structure, meeting both short-term high-power discharge requirements and achieving efficient energy utilization through precise control by the slave controllers.

[0022] 5) Bidirectional energy conversion enhances system dynamic response. IGBT bridge arm redundancy design: Each IGBT upper and lower bridge unit contains 4-6 IGBT modules, with parallel absorption capacitors suppressing switching spikes. It supports bidirectional AC-DC / DC-AC conversion, enabling both overcapacitor charging and rapid injection of active power during grid faults, improving power quality. Multi-stage drive signal conversion: The main control unit precisely controls the IGBT switching sequence through the drive signal conversion board and the first / second IGBT driver board, coupled with a matching unit that monitors module status in real time, achieving low loss and high reliability under high-frequency switching.

[0023] 6) Modular layout and optimized heat dissipation enhance engineering practicality. Functional zoning layout: The overcapacitor mounting rack, film capacitor box, and power heat dissipation box are independently zoned. The overcapacitor unit and supporting capacitor (film capacitor) are separately arranged to reduce electromagnetic interference. The power heat dissipation box integrates heat-generating components such as rectifiers and main control units. It uses a combination of water-cooled plates (inlet / outlet connectors) and cooling fans (DC axial flow fans) for heat dissipation. The temperature measurement unit monitors the temperature in real time and activates a tiered heat dissipation strategy (water cooling + air cooling) to ensure stable component operating temperatures. Port adaptation and cable management: Power transmission port units I / II are equipped with dedicated terminals (overcapacitor positive / negative terminals, power positive / negative terminals, etc.). Standardized cable connections and junction boxes organize power supply lines, improving installation and maintenance efficiency. The film capacitor box and power heat dissipation box are equipped with trays and guide sliders at the bottom for easy movement and fixation.

[0024] 7) Enhanced SVG system performance across multiple dimensions. Strengthened grid support: The overcapacity unit and rectifier unit work together to instantaneously share active power during grid faults, providing inertia support and compensating for the shortcomings of traditional SVG systems that only compensate for reactive power, thus improving system stability. Extended reliability and lifespan: Through precise charge and discharge control, rapid bypass isolation, and optimized heat dissipation design, the risk of component overheating and failure is reduced, extending equipment lifespan. Improved engineering adaptability: The modular structure supports standardized production and installation, and reserved current sensor interfaces and communication ports facilitate system upgrades and remote monitoring, meeting the intelligent requirements of modern power systems. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the main circuit of a preferred mesh-type SVG power unit circuit.

[0026] Figure 2 This is a schematic diagram of a preferred supercapacitor cell and charging circuit;

[0027] Figure 3 This is a schematic diagram of a preferred supporting capacitor unit;

[0028] Figure 4 This is a schematic diagram of a preferred main control unit;

[0029] Figure 5 This is a schematic diagram of a preferred bypass control unit;

[0030] Figure 6 A schematic diagram of the external axial structure of a preferred grid-type SVG power unit device;

[0031] Figure 7 This is a schematic diagram of the internal axonal structure of the power heat sink.

[0032] Figure 8 This is a front view of the internal structure of the power heat sink.

[0033] Figure 9 This is a schematic diagram of the internal structure of the power heat sink from the left.

[0034] Figure 10 This is a schematic diagram comparing the structures on both sides of the water-cooled plate;

[0035] Figure 11 This is a schematic diagram of the axial structure of a thin-film capacitor box;

[0036] Figure 12 A schematic diagram of the axonal structure after the overcapacity unit is installed on the overcapacity mounting frame.

[0037] In the picture:

[0038] 1. Supercapacitor mounting bracket; 2. Thin-film capacitor box; 3. Power heat dissipation box; 3.1 Power box; 3.2 Water-cooled plate; 4. Connecting busbar; 5. IGBT busbar structure; 5.1 IGBT busbar I; 5.2 IGBT busbar II; 6. Auxiliary terminal positive busbar; 7. Auxiliary terminal negative busbar; 8. External copper busbar A; 9. External copper busbar B; 10. Supercapacitor unit; 10.1 Supercapacitor module; 10.2 Photoelectric conversion module; 10.3 Isolation switch 10.4 Main Controller; 10.5 Slave Controller; 10.6 Overcapacity Positive Terminal; 10.7 Overcapacity Negative Terminal; 10.8 Spare Terminal; 11 Capacitor Tray; 12 Power Tray; 13 Guide Slider; 14 Cooling Fan; 15 Water Inlet Connector; 16 Water Outlet Connector; 17 Power Positive Terminal; 18 Power Negative Terminal; 19 Spare Power Terminal; 20 Bypass Contactor I; 21 Discharge Circuit; 22 First Opening 23. Power off; 24. Second switching power supply; 25. Dual power supply module; 26. Junction box; 27. Ventilation hole; 28. Unit control board; 29. ​​PCB board mounting bracket; 20. EMI filter; 31. Absorption capacitor unit I; 32. Absorption capacitor unit II; 33. Diode; 34. Current sensor mounting point; 35. Mechanical bypass control board; 36. Drive signal adapter board; 37. Voltage sampling unit; 38. First IGBT driver board; 49. First IGBT adapter unit; 40. IGBT module; 41. Second IGBT driver board; 42. Second IGBT adapter unit; 41. Equivalent resistance I; 41.1. First resistor; 41.2. Second resistor; 42. Equivalent resistance II; 42.1. Third resistor; 42.2. Fourth resistor; 42.3. Fifth resistor; 42.4. Sixth resistor; 43. Contactor III; 44. Contactor IV; 45. Support capacitor unit. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments.

[0040] Therefore, the following detailed description of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0041] Example 1

[0042] This embodiment discloses a grid-type SVG power unit circuit. As a preferred embodiment of this utility model, it combines technologies such as high-voltage cascading of power electronics, short-time energy storage, and grid control. It can instantaneously share a certain amount of active power during grid faults, providing necessary inertia support for the system. The grid-type SVG power unit circuit includes an overcapacitance unit 10, a main control unit, and a bypass control unit.

[0043] The overcapacity unit 10 is used to provide short-term energy storage, instantaneously sharing active power during grid faults, providing inertia support for the system, and ensuring grid stability. For example... Figure 1 As shown, the overcapacitance unit 10 is provided with a first power transmission terminal (connected to the isolating switch 10.3) and a second power transmission terminal (the RedPow2+ and RedPow2- ports of the overcapacitance unit 10). The first power transmission terminal is connected to the SVG power main circuit through the isolating switch 10.3 to realize energy interaction with the external circuit. The isolating switch 10.3 is used to control the connection status between the first power transmission terminal of the overcapacitance unit 10 and the SVG power main circuit, so as to facilitate disconnection of the circuit during equipment maintenance or fault isolation. The second power transmission terminal (the RedPow2+ and RedPow2- ports of the overcapacitance unit 10) is a backup power supply terminal.

[0044] The SVG power main circuit includes a voltage sampling unit 35, a resistive charging and discharging unit, an EMI filter 28, a supporting capacitor unit 45 (C11), a power supply conversion unit, and a rectifier unit connected in parallel. The second power supply terminal of the overcapacitance unit 10 (the RedPow2+ and RedPow2- ports of the overcapacitance unit 10) is electrically connected to the power supply conversion unit, serving as a backup power supply in case of a fault in the SVG power main circuit, ensuring continuous power supply to critical system units. The power supply conversion unit is connected to the main control unit, the bypass control unit, and the overcapacitance unit 10 for power supply. Specifically, the voltage sampling unit 35 collects the circuit voltage signal in real time and transmits it to the main control unit, providing the main control unit with operating parameter data. The charging function of the resistive charging and discharging unit is used to charge the overcapacitance unit 10 to maintain its energy storage state; the discharging function of the resistive charging and discharging unit is used to discharge the overcapacitance unit 10 and the supporting capacitor unit 45 (C11) before equipment maintenance, eliminating safety hazards caused by residual charge in the capacitors. EMI filter 28 is used to filter electromagnetic interference signals generated in the circuit, ensuring signal purity and improving system reliability. Support capacitor unit 45 (C11), as a core component of reactive power compensation, provides reactive current to the power grid, maintains the power factor, and improves power quality. Furthermore, such as... Figure 3As shown, the supporting capacitor unit 45 (C11) can use a thin-film capacitor C11 with high-current fast charging and discharging characteristics as a reactive power compensation capacitor to realize the reactive power compensation function. The thin-film capacitor C11 is connected in parallel between the DC buses. The majority of the reactive power compensation current is provided by the thin-film capacitor C11, while the active power support is mainly provided by the supercapacitor unit 10. The rectifier unit is responsible for the bidirectional energy conversion (AC-DC / DC-AC) and coordinates the energy flow between the supercapacitor unit 10, the supporting capacitor unit 45 (C11), and the external power grid. The power take-off and transfer unit takes power from the SVG power main circuit and converts it into stable electrical energy to provide normal operating power for the main control unit, bypass control unit, and supercapacitor unit 10. When the SVG power main circuit fails and loses power, the power take-off and transfer unit automatically switches to the second transmission terminal of the supercapacitor unit 10 (the RedPow2 port+ and RedPow2- port of the supercapacitor unit 10) to ensure uninterrupted operation of the system's critical control circuits.

[0045] The main control unit acts as the control center, electrically controlling the voltage sampling unit 35, resistive charging and discharging unit, EMI filter 28, and rectifier unit. It monitors the circuit status in real time and adjusts the operating parameters of each unit to ensure the safe and stable operation of the system. The voltage sampling unit 35 connects to the main control unit via DC15V+, DC15V-, and Udc ports. The EMI filter 28 connects to the main control unit via P and N ports.

[0046] The rectifier unit is connected to external copper busbars A8 and B9 via a bypass control unit. When a fault occurs in the SVG power unit circuit (such as overvoltage, overcurrent, or component damage) and isolation is required, the faulty SVG power unit circuit can be quickly bypassed through the bypass control unit to prevent the fault from spreading and maintain the overall operation of the system.

[0047] Therefore, the working principle of the mesh-type SVG power unit circuit described in this technical solution is as follows:

[0048] Initial startup and normal power supply. After system startup, the power transfer unit obtains electrical energy from the SVG power main circuit, converts it to the appropriate voltage, and then supplies power to the main control unit, bypass control unit, and overcapacitor unit 10, establishing the power foundation for system operation. At this time, the overcapacitor unit 10 charges and stores energy through the resistive charging and discharging unit, supporting the capacitor unit 45 (C11) to perform reactive power compensation tasks under the control of the rectifier unit.

[0049] Emergency power supply in case of failure. When a fault occurs in the SVG power main circuit, causing a power interruption, the power transfer unit detects the abnormality of the main power supply and automatically switches to the second power supply terminal of the overcapacity unit 10 (the RedPow2 port+ and RedPow2- of the overcapacity unit 10) to maintain the operation of the main control unit and the bypass control unit, ensure that the fault handling mechanism (such as bypass isolation) works normally, and avoid secondary faults caused by power failure.

[0050] Energy Interaction and Real-time Control. Normal Operating Conditions: The voltage sampling unit 35 continuously monitors the voltage of the SVG power main circuit and feeds the data back to the main control unit. Based on this, the main control unit adjusts the operating status of the resistive charging / discharging unit, EMI filter 28, and rectifier unit to maintain the energy storage level of the overcapacity unit 10 and the reactive power compensation effect of the system. Fault Operating Conditions: When the grid experiences an active power deficit, the main control unit controls the rectifier unit to release the energy stored in the overcapacity unit 10 to the grid, providing active power support. Simultaneously, the bypass control unit isolates the faulty power unit, ensuring the continuity of power supply to the grid.

[0051] Safety maintenance procedures. Before equipment maintenance, the main control unit controls the resistive charging and discharging unit to discharge the overcapacitor unit 10 and the supporting capacitor unit 45 (C11) to ensure that the capacitor charge is completely released and to ensure the safety of maintenance personnel.

[0052] Furthermore, the above-mentioned network-type SVG power unit circuit can be commercialized into a network-type SVG power unit device, specifically:

[0053] First, divide different functional units into reasonable zones, such as... Figure 6 As shown, the main components include an overcapacitance mounting bracket 1, a thin-film capacitor box 2, a power heat sink box 3, and an external busbar. This partitioned layout is based on the functional characteristics and operational requirements of each unit. The overcapacitance mounting bracket 1 is equipped with a power transmission port unit I, and the power heat sink box 3 is equipped with a power transmission port unit II, an IGBT busbar structure 5, an auxiliary positive busbar 6, an auxiliary negative busbar 7, an external copper busbar A8, and an external copper busbar B9.

[0054] 2. The supercapacitor unit 10 is mounted on the supercapacitor mounting frame 1, and the power transmission terminals (including the first power transmission terminal and the second power transmission terminal) of the supercapacitor unit 10 are connected to the power transmission port unit I. Because the supercapacitor unit 10 needs to provide short-term energy storage and inertia support functions, it has high requirements for power supply stability. Therefore, a separate supercapacitor mounting frame 1 is set up and equipped with the power transmission port unit I to facilitate its energy interaction with external circuits, while avoiding the impact of electromagnetic interference generated by other units during operation on its performance.

[0055] Third, the supporting capacitor unit 45 (C11) is installed in the thin-film capacitor box 2. The supporting capacitor unit 45 (C11) is connected to the IGBT busbar structure 5, the auxiliary positive terminal 6, and the auxiliary negative terminal 7 through an external busbar. As the core component of reactive power compensation, the supporting capacitor unit 45 (C11) is installed in the thin-film capacitor box 2. This not only effectively isolates external interference but also ensures efficient reactive current transmission by tightly connecting it to the IGBT busbar structure 5, the auxiliary positive terminal 6, and the auxiliary negative terminal 7 through the external busbar.

[0056] Fourth, the voltage sampling unit 35, resistive charging and discharging unit, EMI filter 28, power transfer unit, rectifier unit, bypass control unit and main control unit have high requirements for the working environment and there is frequent signal and energy interaction between them. Concentrating them inside the power heat dissipation box 3 not only facilitates the electrical connection between the units, but also facilitates unified heat dissipation management and fault diagnosis.

[0057] V. The electrical connections between each unit must strictly adhere to the design requirements of the above-mentioned network-type SVG power unit circuit to achieve stable energy transmission and signal interaction. This includes:

[0058] 1) The voltage sampling unit 35, resistive charging and discharging unit, EMI filter 28, and power input / output unit are electrically connected to the auxiliary positive busbar 6 and auxiliary negative busbar 7. The rectifier unit is placed inside the power heat sink 3 and connected to the IGBT busbar structure 5. Thus, with the cooperation of the external busbar, IGBT busbar structure 5, auxiliary positive busbar 6, and auxiliary negative busbar 7, the voltage sampling unit 35, resistive charging and discharging unit, EMI filter 28, support capacitor unit 45 (C11), power input / output unit, and rectifier unit are connected in parallel in sequence. Among them, the support capacitor unit 45 (C11) is connected to the IGBT busbar structure 5, auxiliary positive busbar 6, and auxiliary negative busbar 7 through the external busbar, forming a path for reactive power compensation current. The IGBT busbar structure 5, as a key power transmission component, can efficiently transmit the reactive current generated by the support capacitor unit 45 (C11) to the system.

[0059] 2) Connect the two ends of the voltage sampling unit 35 and the power transfer unit to the power transmission port unit II respectively, and then connect the power transmission port unit II and the power transmission port unit I with a cable so that the voltage sampling unit 35 and the power transfer unit are electrically connected to the supercapacitor unit 10 according to the structure of the above-described grid-type SVG power unit circuit.

[0060] 3) Connect the rectifier unit to the external copper busbar A8 and external copper busbar B9 through the bypass control unit; connect the power supply transfer unit to the bypass control unit for power supply; connect the voltage sampling unit 35, the resistive charging and discharging unit, the EMI filter 28 and the rectifier unit to the main control unit for electrical control respectively, and connect the power supply transfer unit to the main control unit for power supply.

[0061] In this technical solution, the power heat dissipation box 3 is designed with the system's heat dissipation requirements in mind. The voltage sampling unit 35, resistive charging / discharging unit, EMI filter 28, power transfer unit, rectifier unit, bypass control unit, and main control unit all generate heat during operation. These components are centrally located inside the power heat dissipation box 3, which is equipped with a robust heat dissipation structure (such as a cooling fan 14 and heat sinks) to effectively dissipate heat and prevent overheating from affecting the performance and lifespan of each unit. Furthermore, this centralized layout facilitates unified testing and repair of all units during equipment maintenance. Before maintenance, the overcapacitor unit 10 and the supporting capacitor unit 45 (C11) can be discharged by the resistive charging / discharging unit controlled by the main control unit, eliminating safety hazards caused by residual capacitor charge and ensuring the safety of maintenance personnel. The clearly defined connection methods and layout of each unit make troubleshooting and replacement of damaged components more convenient and efficient.

[0062] Example 2

[0063] This embodiment discloses a grid-type SVG power unit circuit. As a preferred embodiment of this utility model, based on Embodiment 1, the power supply conversion unit includes a first switching power supply 22 (DCPW1), a second switching power supply 23 (DCPW2), and a dual-power supply module 24 (RedPow). The first input terminal of the dual-power supply module 24 (RedPow) and the input terminal of the second switching power supply 23 (DCPW2) together serve as the first power supply port of the power supply conversion unit and are connected in parallel with the supporting capacitor unit 45 (C11); the second input terminal of the dual-power supply module 24 (RedPow) serves as the power supply conversion unit. The second power input port (RedPow2+ and RedPow2-) of the receiving unit is connected to the second power output terminal (RedPow2+ and RedPow2- ports of the overcapacity unit 10); the input terminal of the first switching power supply 22 (DCPW1) is connected to the output terminal of the dual power supply module 24 (RedPow); the output terminal of the first switching power supply 22 (DCPW1) is the first transfer power supply terminal (DC24V1_+ and DC24V1_0V) of the power input conversion unit, and the output terminal of the second switching power supply 23 (DCPW2) is the second transfer power supply terminal of the power input conversion unit.

[0064] In the circuit structure of the power supply conversion unit described above:

[0065] First, the second switching power supply 23 (DCPW2) draws power from the port connected in parallel with the supporting capacitor unit 45 (C11), and outputs power to supply non-essential control components in the SVG power unit circuit. Additionally, when the network-type SVG power unit circuit is commercialized, a cooling system will be installed to address heat dissipation issues. The first power supply terminals (DC24V1_+ and DC24V1_0V) can also be used to power the cooling system, ensuring the device's heat dissipation requirements are met.

[0066] II. The dual-power supply module 24 (RedPow) serves as a power management hub. Its first input terminal, together with the second switching power supply 23 (DCPW2), is connected to the supporting capacitor unit 45 (C11) to obtain the main power supply. Its second input terminal is connected to the second output terminal of the overcapacitance unit 10 (the RedPow2+ and RedPow2- ports of the overcapacitance unit 10) as a backup power interface. Thus, the status of the two power supplies is monitored in real time, and when the main power supply (powered by the supporting capacitor unit 45) is abnormal, it automatically switches to the backup power supply (powered by the overcapacitance unit 10).

[0067] Third, based on this, the first switching power supply 22 (DCPW1) performs voltage conversion and voltage regulation on the power output from the dual power supply module 24 (RedPow), and outputs a stable adaptive voltage to power the main control units (such as bypass control units, main control units and supercapacitor units 10) of the grid-type SVG power unit circuit, ensuring the stable operation of the core control circuit and ensuring the uninterrupted operation of the system's key functions.

[0068] Based on the functions of each component in the power supply unit described above, the working principle of the power supply unit is as follows:

[0069] I. Normal Power Supply Mode

[0070] Power Acquisition: The first input terminal of the dual power supply module 24 (RedPow) and the second switching power supply 23 (DCPW2) together obtain power from the supporting capacitor unit 45 (C11). After the second switching power supply 23 (DCPW2) converts the power, it supplies power to non-essential control components and cooling systems through the second adapter power supply terminal; the dual power supply module 24 (RedPow) then transmits the power to the first switching power supply 22 (DCPW1).

[0071] Voltage conversion and distribution: The first switching power supply 22 (DCPW1) regulates and adjusts the input power, providing stable power to the main control unit, bypass control unit, and other key control units through the first switching power supply terminals (DC24V1_+ and DC24V1_0V) to maintain the operation of the system's core functions. At this time, the second power supply terminal of the overcapacity unit 10 (the RedPow2 port+ and RedPow2- of the overcapacity unit 10) is in standby mode as a backup power supply, and the dual power supply module 24 (RedPow) continuously monitors the stability of the main power supply.

[0072] II. Emergency Power Supply Mode

[0073] When the power supply to the supporting capacitor unit 45 (C11) is abnormal (such as a voltage drop or interruption caused by a fault in the SVG power main circuit), the dual power supply module 24 (RedPow) quickly detects the failure of the main power supply and triggers the internal switching mechanism to switch the power supply path to the second transmission terminal of the supercapacitor unit 10 (the RedPow2 port+ and RedPow2- port of the supercapacitor unit 10).

[0074] The overcapacity unit 10 serves as a backup power source, continuing to supply power to the first switching power supply terminals (DC24V1_+ and DC24V1_0V) through the dual power supply module 24 (RedPow) and the first switching power supply 22 (DCPW1), ensuring that the main control unit and bypass control unit and other major control units are not affected by power outages, maintaining the system's fault handling capability (such as performing bypass isolation operations), and preventing further deterioration of the fault.

[0075] III. Power Supply Priority and Functional Guarantee

[0076] The power supply transfer unit achieves priority management of power allocation through functional partitioning (the first transfer power supply terminal (DC24V1_+ and DC24V1_0V) ensures core control, while the second transfer power supply terminal serves non-critical loads). The overcapacity unit 10 not only serves as an energy storage element supporting grid inertia but also provides backup power to the power supply transfer unit through the second transmission terminal (the RedPow2+ and RedPow2- ports of the overcapacity unit 10), forming an integrated "energy storage-power supply" collaborative mechanism. When the main power supply is normal, the second switching power supply 23 (DCPW2) supports auxiliary function operation; when the main power supply fails, the backup power supply prioritizes the main control unit, ensuring uninterrupted core system functions and improving overall reliability and fault tolerance.

[0077] Therefore, for the commercialization of the network-type SVG power unit circuit, during the design process of the network-type SVG power unit device, specific port designs were made for transmission port unit II and transmission port unit I to meet the connection requirements of the power supply transfer unit and the overcapacity unit 10. Specifically: transmission port unit II is equipped with a positive power terminal 17, a negative power terminal 18, and a backup power terminal 19; transmission port unit I is equipped with a backup terminal 10.8, a positive overcapacity terminal 10.6, and a negative overcapacity terminal 10.7.

[0078] Therefore, during the hardware deployment and installation process, the deployment and installation of the power supply conversion unit and the voltage sampling unit 35 include: connecting both ends of the voltage sampling unit 35 to the positive power terminal 17 and the negative power terminal 18 respectively, thus realizing the connection of the SVG power main circuit to the positive power terminal 17 and the negative power terminal 18; and connecting the second input terminal of the dual power supply module 24 (RedPow) as the second power supply port (RedPow2+ and RedPow2-) of the power supply conversion unit to the backup power terminal 19. The deployment and installation of the overcapacity unit 10 includes: connecting the first power transmission terminal of the overcapacity unit 10 to the positive overcapacity terminal 10.6 and the negative overcapacity terminal 10.7, and connecting the second power transmission terminal (the RedPow2+ and RedPow2- ports of the overcapacity unit 10) to the backup terminal 10.8. Based on this, the backup power terminal 19 and the backup terminal 10.8 are electrically connected by cables, the positive power terminal 17 is electrically connected to the positive overcapacity terminal 10.6, and the negative power terminal 18 is electrically connected to the negative overcapacity terminal 10.7.

[0079] This port adapter design not only standardizes the connection methods of each unit, but also enhances the reliability and stability of electrical connections through clear terminal definitions and cable connections, reducing the risk of failure caused by connection errors. It also facilitates the maintenance and repair of the equipment in the later stages, improving the practicality and operability of the entire device.

[0080] Example 3

[0081] This embodiment discloses a mesh-type SVG power unit circuit, which is a preferred implementation of this utility model, based on embodiment 1 or 2, such as... Figure 2 As shown, its supercapacitor unit 10 includes a photoelectric conversion module 10.2, a supercapacitor working power supply terminal, an optical fiber signal transmission port (CMSEthNet), a main controller 10.4 (CMS_M), several supercapacitor modules 10.1 (32PCS), and the same number of slave controllers 10.5 (CMS_S) as the supercapacitor modules 10.1 (32PCS).

[0082] like Figure 12As shown, the controllers 10.5 (CMS_S) and the supercapacitor modules 10.1 (32PCS) are electrically connected in a one-to-one correspondence. All the controllers 10.5 (CMS_S) are connected in parallel based on the signal transmission ports (SPI+ and SPI-) and then connected to the control ports (SPI1+ and SPI1-) of the master controller 10.4 (CMS_M). The controller 10.5 (CMS_S) acts as the dedicated manager for the supercapacitor modules 10.1 (32PCS), monitoring key parameters such as voltage, current, and temperature in real time to determine their operating status and promptly uploading the monitoring data to the main controller 10.4 (CMS_M). Based on instructions from the main controller 10.4 (CMS_M), it precisely controls the charging and discharging process of the supercapacitor modules 10.1 (32PCS), performing voltage balancing management to prevent overcharging and over-discharging, ensuring consistent performance across all supercapacitor modules 10.1 (32PCS) and extending their lifespan.

[0083] The communication port of the main controller 10.4 (CMS_M) is connected to the fiber optic signal transmission port (CMSEthNet) via the photoelectric conversion module 10.2. The photoelectric conversion module 10.2 acts as a signal bridge, realizing bidirectional conversion between electrical and optical signals. It converts the electrical signals from the main controller 10.4 (CMS_M) and the slave controller 10.5 (CMS_S) into highly interference-resistant optical signals, which are then transmitted to the external system via the fiber optic signal transmission port (CMSEthNet). Simultaneously, it converts the received optical signals back into electrical signals, ensuring stable data transmission between the supercapacitor unit 10, the main control unit, and the host computer, and preventing electromagnetic interference from affecting the accuracy of control commands and monitoring data. The fiber optic signal transmission port (CMSEthNet) establishes a communication link between the supercapacitor unit 10 and the external system via optical fiber, enabling high-speed and stable transmission of the supercapacitor unit 10's operating status data (voltage, current, temperature, charging and discharging status, etc.) and external control commands, ensuring the timeliness and accuracy of data transmission and providing a reliable basis for system control.

[0084] The main controller 10.4 (CMS_M) serves as the central decision-making unit, receiving real-time status data from each supercapacitor module 10.1 (32PCS) uploaded from the controller 10.5 (CMS_S), and performing comprehensive analysis and processing. Based on instructions issued by the external system, it formulates the overall operation strategy of the supercapacitor unit 10, such as charge and discharge control and fault handling. It communicates with the external system through the photoelectric conversion module 10.2 to coordinate the collaborative work of the supercapacitor unit 10 and the entire SVG power unit circuit.

[0085] The photoelectric conversion module 10.2, the main controller 10.4 (CMS_M), and all slave controllers 10.5 (CMS_S) are connected in parallel via their working power ports (Pwr+ and Pwr- of the photoelectric conversion module 10.2 and slave controller 10.5, and PW terminal of the main controller 10.4) and then connected to the overcapacitive working power terminal. The overcapacitive working power terminal serves as the power hub and the core power interface of the overcapacitive unit 10. It can be connected to the output of the power transfer unit to provide a stable working power supply for the photoelectric conversion module 10.2, the main controller 10.4 (CMS_M), and the slave controllers 10.5 (CMS_S), ensuring the normal operation of the internal control circuitry.

[0086] All 10.1 supercapacitor modules (32 PCS) are connected in series to form a high-capacity energy storage structure. The two ends of this structure are connected to the first transmission terminal and simultaneously to the second transmission terminal (the RedPow2+ and RedPow2- ports of the supercapacitor unit 10). Utilizing its high power density characteristics, rapid energy storage and release are achieved. When the grid is stable, it receives and stores energy; when the grid experiences an active power deficit or fault, it rapidly releases energy and injects it into the SVG power main circuit through the first transmission terminal, providing inertia support and active power compensation to maintain stable grid operation. When the SVG power main circuit fails, the second transmission terminal (the RedPow2+ and RedPow2- ports of the supercapacitor unit 10) maintains power supply to the power transfer unit.

[0087] Based on the functions of each component in the supercapacitor unit 10, the working principle of the supercapacitor unit 10 is as follows:

[0088] I. System Startup and Initialization

[0089] During system startup, the overcapacitance power supply terminals provide power to the photoelectric conversion module 10.2, the main controller 10.4 (CMS_M), and the slave controller 10.5 (CMS_S), enabling them to enter operational status. After completing its self-test, the main controller 10.4 (CMS_M) establishes a communication connection with the external main control unit through the photoelectric conversion module 10.2 and the fiber optic signal transmission port (CMSEthNet), receiving system initialization commands. Simultaneously, it sends a self-test command to the slave controller 10.5 (CMS_S) to ensure that all components are ready, laying the foundation for subsequent operation.

[0090] II. Real-time monitoring and data acquisition

[0091] The controller 10.5 (CMS_S) continuously collects real-time data such as voltage, current, and temperature from the corresponding supercapacitor modules 10.1 (32PCS) and uploads the data to the main controller 10.4 (CMS_M) via parallel signal transmission lines. The main controller 10.4 (CMS_M) summarizes and performs preliminary analysis on the data to determine whether there are any abnormalities in each supercapacitor module 10.1 (32PCS) (such as voltage imbalance, excessive temperature, abnormal current, etc.), providing data support for the formulation of subsequent control strategies.

[0092] III. Energy Management and Coordinated Control

[0093] Charging process: During normal grid operation, the resistive charging and discharging unit charges the supercapacitor modules 10.1 (32PCS). The controller 10.5 (CMS_S) dynamically adjusts the charging parameters (such as current and voltage) based on the real-time status of the supercapacitor modules 10.1 (32PCS) to ensure a safe and efficient charging process. The main controller 10.4 (CMS_M) monitors the overall charging progress and interacts with the external main control unit to optimize the charging strategy, achieving balanced charging of each supercapacitor module 10.1 (32PCS) and improving energy storage efficiency.

[0094] Discharge Process: When the power grid experiences an active power deficit or fault, the main controller 10.4 (CMS_M) receives a discharge command sent by the external main control unit through the fiber optic signal transmission port (CMSEthNet) and quickly issues a discharge command to the slave controller 10.5 (CMS_S). The slave controller 10.5 (CMS_S) controls the supercapacitor module 10.1 (32PCS) to rapidly release the stored electrical energy, which is injected into the SVG power main circuit through the first transmission terminal to provide active power support for the system. During the discharge process, the slave controller 10.5 (CMS_S) continuously monitors the parameters of the supercapacitor module 10.1 (32PCS) to prevent over-discharge, and the main controller 10.4 (CMS_M) adjusts the discharge strategy based on real-time data to ensure a stable and safe discharge process.

[0095] IV. Fault Monitoring and Handling

[0096] If the controller 10.5 (CMS_S) detects an abnormality in the supercapacitor module 10.1 (32PCS) (such as excessive single-cell voltage deviation, excessive temperature, internal short circuit, etc.), it immediately reports the fault information to the main controller 10.4 (CMS_M). The main controller 10.4 (CMS_M) issues instructions to the slave controller 10.5 (CMS_S) according to the preset fault handling strategy (such as activating the equalization circuit, limiting charging and discharging current, isolating the faulty module, etc.). If the fault is severe, the main controller 10.4 (CMS_M) relays feedback to the external main control unit through the fiber optic signal transmission port (CMSEthNet), requesting further processing to ensure the safe operation of the supercapacitor unit 10 and the entire circuit.

[0097] V. Communication Interaction and System Collaboration

[0098] The photoelectric conversion module 10.2 converts the electrical signals from the main controller 10.4 (CMS_M) and the slave controller 10.5 (CMS_S) into optical signals, enabling high-speed communication with external systems via the fiber optic signal transmission port (CMSEthNet). The main controller 10.4 (CMS_M) receives control commands from the external main control unit and adjusts the operating strategy of the supercapacitor unit 10 in a timely manner. Simultaneously, it uploads the operating data of the supercapacitor unit 10 (voltage, current, charging and discharging status, health status, etc.) to the external system, facilitating remote monitoring and management by maintenance personnel and achieving efficient collaboration between the supercapacitor unit 10 and the entire SVG power unit circuit.

[0099] Therefore, for the commercialization of the network-type SVG power unit circuit, in the design process of the network-type SVG power unit device, based on the circuit structure of the supercapacitor unit 10 and the connection requirements of the supercapacitor unit 10, the supercapacitor unit 10 is arranged on the supercapacitor mounting frame 1. This includes: arranging all supercapacitor modules 10.1 (32PCS) neatly in two rows on the supercapacitor mounting frame 1. This layout makes full use of space and facilitates heat dissipation, reducing the impact of heat accumulation between modules on performance. All slave controllers 10.5 (CMS_S) are installed one-to-one with the supercapacitor modules 10.1 (32PCS) to avoid wiring errors; and the slave controllers 10.5 (CMS_S) are electrically connected one-to-one with the supercapacitor modules 10.1 (32PCS) to ensure real-time monitoring and precise control of each supercapacitor module 10.1 (32PCS), realizing rapid acquisition and feedback of parameters such as voltage, current, and temperature. The main controller 10.4 (CMS_M) and the photoelectric conversion module 10.2 are fixed on the overcapacity mounting bracket 1. The communication port of the main controller 10.4 (CMS_M) is connected to the fiber optic signal transmission port (CMSEthNet) through the photoelectric conversion module 10.2. All slave controllers 10.5 (CMS_S) are connected in parallel via cables through their signal transmission ports (SPI+ and SPI-), and then connected to the control ports (SPI1+ and SPI1-) of the main controller 10.4 (CMS_M). The photoelectric conversion module 10.2, the main controller 10.4 (CMS_M), and all slave controllers 10.5 (CMS_S) are connected in parallel via cables through their power supply ports (Pwr+ and Pwr-), and then connected to the overcapacity power supply terminals. The disconnect switch 10.3 is fixed to the supercapacitor mounting bracket 1. All supercapacitor modules 10.1 (32 PCS) are connected in series with cables and then connected to the spare terminal 10.8. At the same time, they are connected to the positive terminal 10.6 and the negative terminal 10.7 of the supercapacitor side through the disconnect switch 10.3. The cable connections between the components adopt standardized interfaces and fixing methods, which enhances the reliability of electrical connections and reduces the risk of failure due to poor contact. Clear wiring and port labeling also facilitate later fault diagnosis and component replacement, improving equipment maintenance efficiency and convenience.

[0100] Example 4

[0101] This embodiment discloses a grid-type SVG power unit circuit. As a preferred embodiment of this utility model, based on embodiments 1, 2, or 3, its resistive charging and discharging unit includes a charging circuit and a discharging circuit 21. One end of the charging circuit is connected to the negative terminal of the first power supply terminal of the supercapacitor unit 10 through the isolating switch 10.3, and the other end of the charging circuit is connected to one end of the charging circuit. The other end of the charging circuit is connected to the positive terminal of the first power supply terminal of the supercapacitor unit 10 through the isolating switch 10.3.

[0102] Based on this, a Hall current sensor can be installed on the DC bus to monitor the DC bus current. Since all SVG power units in a single phase are connected in series, the AC current of each unit is equal. By controlling the DC voltage of each SVG power unit, the DC current of each SVG power unit can be balanced. Considering practical engineering, monitoring the DC current of each SVG power unit is not very meaningful, and the current does not participate in the control process. Therefore, only a current sensor mounting position is reserved in the SVG power unit, specifically a current sensor mounting point 32 is set between the charging circuit and the discharging circuit 21. In practice, this sensor is not installed; the DC current can be obtained through power conversion. The connection ports between the current sensor mounting point 32 and the main control unit are DCCurrTransPwr+, DCCurrTransPwr-, and DCCurrTransOut.

[0103] Example 5

[0104] This embodiment discloses a grid-type SVG power unit circuit. As a preferred embodiment of this utility model, based on embodiment 4, to achieve supercapacitor charging while considering the charging time, the charging circuit is set with two-stage charging, including equivalent resistor I41 (R1), equivalent resistor II42 (R2), contactor III43 (K3), and reactor (L1) connected in series. Contactor IV44 (K4) is connected in parallel across the equivalent resistor I41 (R1), and diode 31 (V1) is connected in parallel across the series circuit formed by equivalent resistor I41 (R1), equivalent resistor II42 (R2), and contactor III43 (K3). Further, the discharge circuit 21 is composed of resistor III (R3), resistor IV (R4), and resistor V (R5) connected in series.

[0105] In the above charging circuit, the equivalent resistor II42 (R2) participates in current limiting in both stages of the charging circuit. During the first stage of charging, it is connected in series with the equivalent resistor I41 (R1), while during the second stage, it operates independently, coordinating with segmented adjustment of the charging voltage to control the charging rate and duration. Contactor III43 (K3) controls the on / off state of the charging circuit. When energized, it connects to the equivalent resistor I41 (R1), the equivalent resistor II42 (R2), and the reactor (L1) to initiate the charging process; it remains energized to maintain the circuit continuity during the continuous current charging stage, replenishing the supercapacitor's energy. Contactor IV44 (K4) is connected in parallel across the equivalent resistor I41 (R1). When energized, it short-circuits the equivalent resistor I41 (R1), switching the charging circuit from the first stage to the second stage, changing the charging resistor value, and achieving segmented charging voltage switching. The reactor (L1) is connected in series in the charging circuit to suppress sudden changes in charging current, reduce the impact of current fluctuations on the circuit, and improve the stability of the charging process. Diode 31 (V1) is connected in parallel across the series circuit of equivalent resistor I41 (R1), equivalent resistor II42 (R2), and contactor III43 (K3) to form a freewheeling path. When the charging circuit is disconnected or the current changes suddenly, it releases the energy stored in the inductor (reactor (L1)) and protects the circuit components from back electromotive force.

[0106] First-stage charging: The initial voltage of the supercapacitor is low (e.g., not reaching 760V), contactor III43 (K3) engages, and contactor IV44 (K4) disengages. Equivalent resistor I41 (R1) + equivalent resistor II42 (R2) + reactor (L1) are connected in series in the charging circuit. In practical applications, the equivalent resistance of equivalent resistor I41 (R1) can be 15Ω, and the equivalent resistance of equivalent resistor II42 (R2) can be 80Ω. Thus, the charging resistor value for the first stage of charging is 95Ω. The first-stage charging voltage can be set to 800V, and the charging termination voltage to 760V.

[0107] Second-stage charging: After the supercapacitor voltage reaches 760V, contactor IV44 (K4) engages, short-circuiting the equivalent resistance I41 (R1). The equivalent resistance II42 (R2) and reactor (L1) are connected in series in the charging circuit. Thus, in the second-stage charging circuit, the charging resistance value drops to 80Ω of the equivalent resistance II42 (R2). The second-stage charging voltage can be set to 1000V, and the charging end voltage to 950V. The charging stage is considered complete when the supercapacitor unit 10 voltage reaches 950V, and the calculated charging time does not exceed 20 minutes. Subsequently, during the freewheeling charging phase, contactors III43 (K3) and IV44 (K4) remain engaged (equivalent resistor I41 (R1) is still short-circuited), while equivalent resistor II42 (R2) and reactor (L1) remain connected to the circuit. Through the freewheeling channel of diode 31 (V1) in conjunction with reactor (L1), the voltage of supercapacitor unit 10 is gradually increased to 1000V and maintained at this voltage level. During this time, contactors III43 (K3) and equivalent resistor II42 (R2) are connected for an extended period to compensate for the energy consumption of the supercapacitor during operation, ensuring voltage stability.

[0108] Protection mechanism: When the charging circuit is disconnected (such as when contactor Ⅲ43 (K3) operates), diode 31 (V1) provides a freewheeling path for reactor (L1) to prevent back EMF from damaging the components; the two-stage resistor switching and reactor (L1) current limiting, combined with segmented voltage control, ensure charging efficiency and avoid current surges, thereby improving system safety and reliability.

[0109] Therefore, for the commercialization of mesh-type SVG power unit circuits, in the design process of mesh-type SVG power unit devices, such as Figure 2 As shown, the system includes: a first resistor 41.1 (R11) and a second resistor 41.2 (R12) connected in parallel to form an equivalent resistor I 41 (R1), where the resistance of the first resistor 41.1 (R11) and the second resistor 41.2 (R12) is 30Ω. A third resistor 42.1 (R21), a fourth resistor 42.2 (R22), a fifth resistor 42.3 (R23), and a sixth resistor 42.4 (R24) connected in series to form an equivalent resistor II 42 (R2), where the resistance of the third resistor 42.1 (R21), the fourth resistor 42.2 (R22), the fifth resistor 42.3 (R23), and the sixth resistor 42.4 (R24) is 20Ω. This combination method allows for precise control of the resistance value and facilitates the implementation of complex resistance value requirements using standard resistor components. The layout of each resistor component within the power heat sink 3 follows the principle of prioritizing heat dissipation, with spacing to avoid heat concentration and reduce the risk of resistance performance degradation due to excessive temperature. Then, the series equivalent resistor I41 (R1), equivalent resistor II42 (R2), contactor III43 (K3), reactor (L1), contactor IV44 (K4) and diode 31 (V1) are connected according to the structure of the charging circuit described above.

[0110] Example 6

[0111] This embodiment discloses a network-type SVG power unit circuit. As a preferred embodiment of this utility model, based on any one of embodiments 1 to 5, its bypass control unit includes a mechanical bypass control board 33, a bypass contactor I 20 (K1), and a contactor II (K2). The mechanical bypass control board 33 is provided with an optical fiber communication port for communicating with an external system (host computer), receiving and parsing bypass commands, and realizing the transmission and processing of remote control signals. The power terminals (KCtrl1+ and KCtrl1-) of the mechanical bypass control board 33 are electrically connected to the power supply conversion unit (first conversion power supply terminal) to obtain working power and ensure the normal operation of the control logic.

[0112] The coil and auxiliary contacts of contactor II (K2) are connected to the mechanical bypass control board 33 (JP2 terminal). The two ends (KCtrl2+ and KCtrl2-) of the series circuit between the auxiliary contacts of contactor II (K2) and the coil of bypass contactor I 20 (K1) are electrically connected to the power supply transfer unit (first transfer power supply terminal). In addition, the mechanical bypass control board 33 is also provided with fiber optic communication ports (OPT1 and OPT2) for communication with external systems (such as host computers) to realize data interaction and related command reception. The control logic involved in this structure is as follows: output control signals to the coil of contactor II (K2), and indirectly control the on / off state of bypass contactor I 20 (K1) through the action of contactor II (K2) to realize the bypass control logic. Specifically, contactor II (K2) serves as an intermediate control hub. Its coil is driven by the signal from mechanical bypass control board 33. After its auxiliary contacts are activated, they connect the coil power supply of bypass contactor I20 (K1), thereby achieving electrical isolation and amplification between the control signal and the actuator.

[0113] The rectifier unit is connected to external copper busbars A8 and B9 via bypass contactor I20 (K1). When the coil of bypass contactor I20 (K1) is energized, its contacts actuate, bypassing the rectifier unit and allowing the current to flow directly through the external copper busbars A8 and B9, thus preventing the rectifier unit from participating in the operation (e.g., isolating the rectifier unit in case of a fault).

[0114] Example 7

[0115] This embodiment discloses a grid-type SVG power unit circuit. As a preferred embodiment of this utility model, based on embodiment 6, its rectifier unit includes an IGBT upper bridge unit (such as IGBT1~6), an IGBT lower bridge unit (such as IGBT7~12), a first IGBT adapter unit 37 (such as IGBT board 1~6), and a second IGBT adapter unit 40 (such as IGBT board 7~12).

[0116] The IGBT upper-bridge units (such as IGBT1~6) and IGBT lower-bridge units (such as IGBT7~12) are connected in parallel to form an H-bridge or three-phase bridge structure, realizing bidirectional energy conversion between AC-DC and DC-AC. Through high-frequency on / off control of the IGBT modules 38, DC power is inverted into AC power and injected into the grid (inverter mode), or AC power is rectified into DC power and stored in the overcapacity unit 10 (rectifier mode). The IGBT upper-bridge units (such as IGBT1~6) contain four or six IGBT modules 38, and the IGBT lower-bridge units contain the same number of IGBT modules 38 as the IGBT upper-bridge units (such as IGBT1~6). This redundant design of four or six IGBT modules 38 improves power capacity and system reliability, allowing operation to continue even if a single IGBT module 38 fails.

[0117] All IGBT modules 38 in the IGBT upper bridge unit (e.g., IGBT1~6) are respectively connected to the first IGBT adapter unit 37 (e.g., IGBT boards 1~6), and all IGBT modules 38 in the IGBT lower bridge unit (e.g., IGBT7~12) are respectively connected to the second IGBT adapter unit 40 (e.g., IGBT boards 7~12). The first IGBT adapter unit 37 (e.g., IGBT boards 1~6) and the second IGBT adapter unit 40 (e.g., IGBT boards 7~12) provide precise drive signals to the corresponding bridge arm IGBT modules 38 to control the switching timing; at the same time, they monitor the operating status of the IGBTs (e.g., overcurrent, overvoltage, temperature) and quickly shut down the modules in case of abnormalities to protect the circuit safety.

[0118] The IGBT upper bridge unit (e.g., IGBT1~6) has absorption capacitor unit I29 (e.g., C1~6) connected in parallel across its two ends, and the IGBT lower bridge unit (e.g., IGBT7~12) has absorption capacitor unit II30 (e.g., C7~12) connected in parallel across its two ends. The number of absorption capacitors in absorption capacitor unit I29 (e.g., C1~6) and absorption capacitor unit II30 (e.g., C7~12) is consistent with the number of IGBT modules 38 in the IGBT upper bridge unit (e.g., IGBT1~6) and IGBT lower bridge unit (e.g., IGBT7~12). The absorption capacitors are connected in parallel across the two ends of the IGBT module 38 in a one-to-one correspondence, absorbing the voltage spikes generated during the switching process of the IGBT module 38, reducing switching losses, reducing electromagnetic interference, and protecting the IGBT module 38 from excessive voltage surges.

[0119] Based on this, the bypass contactor I20 (K1) includes normally open and normally closed contacts that are interconnected. The IGBT upper bridge unit (e.g., IGBT1~6) is directly connected to the external copper busbar A8, and the IGBT lower bridge unit (e.g., IGBT7~12) is connected to the external copper busbar B9 through the normally closed contact of the bypass contactor I20 (K1); the external copper busbar A8 is connected to the external copper busbar B9 through the normally open contact of the bypass contactor I20 (K1). Normally closed contact: Closed during normal operation, connecting the IGBT lower bridge unit (e.g., IGBT7~12) to the external copper busbar B9, allowing the rectifier unit to participate in energy conversion. Normally open contact: Closed in case of a fault, directly connecting the external copper busbar A8 to B9, bypassing the rectifier unit, and ensuring the power unit continues to operate (at this time, the overcapacitance unit 10 does not participate, only transmitting power through the copper busbar).

[0120] Therefore, the working principle of the rectifier unit is as follows:

[0121] I. Normal working mode (bypass contactor I20 (K1) normally closed contact closed, normally open contact open)

[0122] Rectification Mode (Grid → Overcapacity Unit 10): AC power from the grid is input via external copper busbars A8 and B9. IGBT modules 38 in the IGBT upper bridge unit (e.g., IGBT1~6) and IGBT lower bridge unit (e.g., IGBT7~12) are turned on / off according to a specific timing sequence (e.g., SPWM control), rectifying the AC power into DC power. The DC power then charges the overcapacity unit 10 through a charging circuit, achieving energy storage.

[0123] Inverter Mode (Overcapacitor Unit 10 → Grid): When the overcapacitor unit 10 discharges, the DC power is inverted into AC power through the IGBT bridge arm. The amplitude and phase of the output voltage are adjusted by PWM control to inject active power into the grid or provide reactive power compensation. Absorption capacitor units I 29 (e.g., C1~6) and II 30 (e.g., C7~12) suppress voltage spikes during the switching process of the IGBT module 38, ensuring switching safety.

[0124] II. Fault Bypass Mode (Bypass Contactor I20 (K1) normally closed contact open, normally open contact closed)

[0125] When the rectifier unit detects a fault (such as IGBT over-temperature or short circuit), the bypass control unit triggers the bypass contactor I20 (K1) to operate: the normally closed contact opens, disconnecting the connection between the IGBT lower bridge unit (such as IGBT7~12) and the external copper busbar B9; the normally open contact closes, directly connecting the external copper busbar A8 and the external copper busbar B9, forming a low-impedance bypass path. At this time, the rectifier unit is isolated, and the power unit continues to transmit electrical energy through the copper busbar to maintain system operation (but loses energy conversion and reactive power compensation capabilities).

[0126] Example 8

[0127] This embodiment discloses a mesh-type SVG power unit circuit. As a preferred embodiment of this utility model, based on embodiment 7, its main control unit includes a unit control board 26, a drive signal adapter board 34, a first IGBT drive board 36, and a second IGBT drive board 39. The drive signal adapter board 34 is electrically connected to the unit control board 26, and simultaneously electrically connected to the first IGBT adapter unit 37 (such as IGBT boards 1-6) through the first IGBT drive board 36, and electrically connected to the second IGBT adapter unit 40 (such as IGBT boards 7-12) through the second IGBT drive board 39. The voltage sampling unit 35, the resistive charging and discharging unit, and the EMI filter 28 are respectively electrically connected to the unit control board 26. Figure 5 As shown, in the unit control board 26, connector CN1 is used to connect to EMI filter 28, connector CN8 is used to connect to voltage sampling unit 35, connector CN9 is used to connect to Hall current sensor, connector CN10 is used to connect to contactor Ⅲ43 (K3) in resistive charging and discharging unit, connector CN11 is used to connect to contactor Ⅳ44 (K4) in resistive charging and discharging unit, connector CN7 is used to connect to drive signal adapter board 34, and connector CN4 is set with working power ports (CtrlMPwr+ and CtrlMPwr-) for connecting to power supply adapter unit (first adapter power supply terminal).

[0128] The unit control board 26 is the core decision-making center of the SVG power unit circuit, possessing functions including but not limited to the following: It can calculate the grid state (voltage, frequency, phase) and the state of charge (SOC) of the overcapacitor unit 10 based on data from the voltage sampling unit 35, generating a control strategy; it can regulate the charging and discharging state by controlling the on / off state of contactors III 43 (K3) and IV 44 (K4) in the resistive charging and discharging unit; it can adjust the parameters of the EMI filter 28 to suppress interference, and simultaneously control the energy conversion process of the rectifier unit through the drive signal adapter board 34. In addition, the unit control board 26 is equipped with fiber optic communication ports (OPT1 and OPT2) for communication with external systems (such as a host computer) to achieve data interaction and related command reception. The core function of the drive signal adapter board 34 is signal conversion and distribution, converting the digital control signals output by the unit control board 26 into level signals adapted to the IGBT driver boards, and simultaneously distributing them to the first IGBT driver board 36 and the second IGBT driver board 39 to achieve signal isolation and enhancement. The first IGBT driver board 36 and the second IGBT driver board 39 are used for precise IGBT driving. They provide high-power, low-latency drive signals to the IGBT modules 38 of the IGBT upper bridge unit (such as IGBT1~6) and the IGBT lower bridge unit (such as IGBT7~12) to control the switching timing and turn-on / turn-off rate.

[0129] Based on this, for the commercialization of the network-type SVG power unit circuit, in the design process of the network-type SVG power unit device, considering the IGBT module 38, the resistors in the charging circuit, and the diode 31 (V1) as the main heat-generating components, the power heat dissipation box 3 is set up, including setting up a power box 3.1, in which a temperature measuring unit and a water-cooled plate 3.2 are set up, and the water-cooled plate 3.2 is equipped with a water inlet connector 15 and a water outlet connector 16; then the rectifier unit is arranged inside the power heat dissipation box 3, such as... Figure 7 and Figure 9 As shown, this includes: mounting the IGBT upper bridge unit (such as IGBT1~6) together with IGBT busbar I 5.1 on one side of the water-cooled plate 3.2; mounting the IGBT lower bridge unit (such as IGBT7~12) together with IGBT busbar II 5.2 on the other side of the water-cooled plate 3.2; and electrically connecting the temperature measuring unit to the main control unit. Further, as... Figure 10 As shown, the equivalent resistors I41 (R1) and II42 (R2) in the charging circuit are respectively arranged on both sides of the water-cooled plate 3.2. This approach simplifies the thermal management design, mechanical layout, and electrical connection of the SVG power unit, making the entire SVG power unit more compact, lightweight, and easier to install and maintain. It also improves the operating temperature environment of the SVG power unit, thereby enhancing its stability and lifespan.

[0130] Furthermore, considering the presence of other heat-generating components, although their heat output is not significant, air cooling is incorporated into the design of the power heat dissipation box 3. Specifically, a cooling fan 14 is embedded in the power box 3.1, and ventilation holes 25 are provided. The cooling fan 14 is electrically connected to both the main control unit and the power supply unit. The cooling fan 14 can be a DC axial fan.

[0131] Furthermore, if a heat dissipation and cooling system (temperature measuring unit, cooling fan 14, etc.) is installed inside the power heat dissipation box 3, such as Figure 11As shown, in the unit control board 26: connectors CN5 and CN6 are used to connect the cooling fan 14; connector CN2 is used to connect the ground loop probe (RT1) of the negative temperature coefficient thermistor in the temperature measurement unit; the temperature control contact (RT3) controlled by the negative temperature coefficient thermistor is connected in series with the normally closed temperature relay (TR2) to form a temperature relay combination, and connector CN3 is used to connect this temperature relay combination. Thus, the temperature measurement unit uses a negative temperature coefficient (NTC) thermistor (such as RT1) as a temperature sensor to monitor the temperature changes inside the power box 3.1 in real time, thereby controlling the operation of the temperature relay combination and achieving temperature threshold trigger control. This allows for the preset high-temperature and low-temperature heat dissipation stages according to actual needs: In the low-temperature heat dissipation stage (e.g., <70℃), the water cooling system circulates normally, and the unit control board 26 controls the cooling fan 14 to run at a slow speed or start only one cooling fan 14 via connection CN5 and / or connector CN6. The water cooling plate 3.2 dissipates heat from the rectifier unit and the resistive elements and diodes 31 (V1) in the charging circuit, while the cooling fan 14 dissipates heat from other heat-generating components (such as contactors) in the power heat sink 3. In the high-temperature heat dissipation stage (e.g., ≤70℃), the unit control board 26 controls both cooling fans 14 to start at full speed via connection CN5 and connector CN6. Simultaneously, the unit control board 26 adjusts the water cooling system flow rate or pressure to enhance heat dissipation efficiency. Air cooling and water cooling work together to accelerate heat dissipation. If the temperature continues to rise to 85℃, a combination of temperature relays is triggered, and the system enters a protection mode (e.g., reducing the output power of the SVG power unit).

[0132] Example 9

[0133] This embodiment discloses a mesh-type SVG power unit circuit. As a preferred embodiment of this utility model, based on any of embodiments 1-8, for the commercialization of the mesh-type SVG power unit circuit, during the design process of the mesh-type SVG power unit device, such as... Figure 11 As shown, considering the transportation, installation, and moisture protection of the SVG power unit device, a power tray 12 is installed at the bottom of the power heat dissipation box 3, and a capacitor tray 11 is installed at the bottom of the film capacitor box 2. A guide slider 13 is used to fixably and slidably connect the film capacitor box 2 and the capacitor tray 11. A handle is provided on the front side of the film capacitor box 2. Figure 7 and Figure 8As shown, considering the power supply line layout from the power transfer unit inside the power heat dissipation box 3 to each unit, a junction box 24 is installed to improve the neatness of the cables. To improve the space utilization inside the power heat dissipation box 3, while also taking into account the space spacing between each unit, a PCB board mounting bracket 27 is installed inside the power box 3.1 to mount some PCB integrated boards (such as the unit control board 26, mechanical bypass control board 33, EMI filter 28, voltage sampling unit 35, and drive signal adapter board 34, etc.) on the PCB board mounting bracket 27.

Claims

1. A grid forming SVG power cell circuit, characterized by: It includes an overcapacitance unit (10), a main control unit, and a bypass control unit; the overcapacitance unit (10) is provided with a first power supply terminal and a second power supply terminal, the first power supply terminal is connected in parallel with a voltage sampling unit (35), a resistive charging and discharging unit, an EMI filter (28), a supporting capacitor unit (45), a power take-off conversion unit, and a rectifier unit through an isolating switch (10.3), and the second power supply terminal is electrically connected to the power take-off conversion unit; the voltage sampling unit (35), the resistive charging and discharging unit, the EMI filter (28), and the rectifier unit are respectively electrically controlled and connected to the main control unit; the rectifier unit is connected to an external copper busbar A (8) and an external copper busbar B (9) through the bypass control unit; the power take-off conversion unit is connected to the main control unit, the bypass control unit, and the overcapacitance unit (10) for power supply.

2. A networked SVG power cell circuit as recited in claim 1, wherein: The power supply conversion unit includes a first switching power supply (22), a second switching power supply (23), and a dual-power supply module (24); the first input terminal of the dual-power supply module (24) and the input terminal of the second switching power supply (23) together serve as the first power supply port of the power supply conversion unit and are connected in parallel with the supporting capacitor unit (45); the second input terminal of the dual-power supply module (24) serves as the second power supply port of the power supply conversion unit and is connected to the second power transmission terminal of the overcapacitor unit (10); the input terminal of the first switching power supply (22) is connected to the output terminal of the dual-power supply module (24); the output terminal of the first switching power supply (22) is the first conversion power supply terminal of the power supply conversion unit, and the output terminal of the second switching power supply (23) is the second conversion power supply terminal of the power supply conversion unit.

3. The grid-type SVG power unit circuit as described in claim 1, characterized in that: The supercapacitor unit (10) includes a photoelectric conversion module (10.2), a supercapacitor working power supply terminal, an optical fiber signal transmission port, a main controller (10.4), several supercapacitor modules (10.1), and the same number of slave controllers (10.5) as the supercapacitor modules (10.1). The slave controllers (10.5) are electrically connected to the supercapacitor modules (10.1) in a one-to-one correspondence. All slave controllers (10.5) are connected in parallel based on the signal transmission ports and then connected to the control port of the main controller (10.4). The communication port of the main controller (10.4) is connected to the optical fiber signal transmission port through the photoelectric conversion module (10.2). The photoelectric conversion module (10.2), the main controller (10.4), and all slave controllers (10.5) are connected in parallel based on the working power supply ports and then connected to the supercapacitor working power supply terminal. The two ends of all supercapacitor modules (10.1) connected in series are connected to the first power transmission terminal and simultaneously connected to the second power transmission terminal.

4. The networked SVG power cell circuit of claim 1, wherein: The resistive charging and discharging unit includes a charging circuit and a discharging circuit (21); one end of the charging circuit is connected to the negative terminal of the first power supply terminal of the supercapacitor unit (10) through the isolating switch (10.3), and the other end of the charging circuit is connected to one end of the charging circuit. The other end of the charging circuit is connected to the positive terminal of the first power supply terminal of the supercapacitor unit (10) through the isolating switch (10.3); a current sensor mounting point (32) is provided between the charging circuit and the discharging circuit (21).

5. The grid-type SVG power unit circuit as described in claim 4, characterized in that: The charging circuit includes an equivalent resistor I (41), an equivalent resistor II (42), a contactor III (43), and a reactor connected in series. A contactor IV (44) is connected in parallel across the equivalent resistor I (41), and a diode (31) is connected in parallel across the series circuit consisting of the equivalent resistor I (41), the equivalent resistor II (42), and the contactor III (43).

6. The grid-type SVG power unit circuit as described in claim 5, characterized in that: In the charging circuit: the equivalent resistance I (41) is formed by the first resistor (41.1) and the second resistor (41.2) connected in parallel; the equivalent resistance II (42) is formed by the third resistor (42.1), the fourth resistor (42.2), the fifth resistor (42.3) and the sixth resistor (42.4) connected in series.

7. The grid-type SVG power unit circuit as described in claim 4, characterized in that: The discharge circuit (21) is composed of resistors III, IV and V connected in series.

8. The grid-type SVG power unit circuit as described in claim 1, characterized in that: The bypass control unit includes a bypass control board, bypass contactor I (20) and contactor II, and the power supply terminals of the bypass control board are electrically connected to the power supply transfer unit. The coil of contactor II and the auxiliary contacts of contactor II are respectively connected to the bypass control board; The auxiliary contact of contactor II is electrically connected to the power transfer unit via a series circuit with the coil of bypass contactor I (20); the rectifier unit is connected to external copper busbar A (8) and external copper busbar B (9) via bypass contactor I (20).

9. The grid-type SVG power unit circuit as described in claim 8, characterized in that, The rectifier unit includes an IGBT upper bridge unit, an IGBT lower bridge unit, a first IGBT adapter unit (37), and a second IGBT adapter unit (40). The IGBT upper bridge unit and the IGBT lower bridge unit are connected in parallel. The IGBT upper bridge unit contains four or six IGBT modules (38), and the IGBT lower bridge unit contains the same number of IGBT modules (38) as the IGBT upper bridge unit. All IGBT modules (38) in the IGBT upper bridge unit are respectively connected to the first IGBT adapter unit (37), and all IGBT modules (38) in the IGBT lower bridge unit are respectively connected to the second IGBT adapter unit (40). An absorption capacitor unit I (29) is connected in parallel across the two ends of the IGBT upper bridge unit, and an absorption capacitor unit II (30) is connected in parallel across the two ends of the IGBT lower bridge unit.

10. The grid-type SVG power unit circuit as described in claim 9, characterized in that: The bypass contactor I (20) includes normally open contacts and normally closed contacts that are interconnected; the IGBT upper bridge unit is directly connected to the external copper busbar A (8), and the IGBT lower bridge unit is connected to the external copper busbar B (9) through the normally closed contact of the bypass contactor I (20); the external copper busbar A (8) is connected to the external copper busbar B (9) through the normally open contact of the bypass contactor I (20).

11. The grid-type SVG power unit circuit as described in claim 9, characterized in that: The main control unit includes a unit control board (26), a drive signal adapter board (34), a first IGBT drive board (36), and a second IGBT drive board (39). The drive signal adapter board (34) is electrically connected to the unit control board (26), and is electrically connected to the first IGBT adapter unit (37) through the first IGBT drive board (36), and is electrically connected to the second IGBT adapter unit (40) through the second IGBT drive board (39). The voltage sampling unit (35), the resistive charging and discharging unit, and the EMI filter (28) are electrically connected to the unit control board (26) respectively.

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